Drill string member

ABSTRACT

A drill string member is formed by providing a former and a cylindrical member to be shaped in relationship with the former. Seals are provided between opposing ends of a thick wall cylinder and the cylindrical member, a pressure is applied in the annulus between the cylindrical member and the thick wall cylinder sufficient to deform the cylindrical member against the former. The drill string member thus formed has a constant wall thickness and a non-circular former provides a non-circular drill string member.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of Great Britain patent applicationSer. No. 0024909.4, filed on Oct. 11, 2000.

BACKGROUND OF THE INVENTION

1) Field of the Invention

This invention relates to a drill string member and particularly to adrill string member arranged to alleviate or prevent differentialsticking downhole.

2) Description of the Related Art

It is known from the Society of Petroleum Engineers, Paper SPE22549,“Differential Sticking Laboratory Tests can improve Mud Design” by M.Bushnell-Watson and S. S. Panesar, presented to the 66^(th) AnnualConference and Exhibition of the Society of Petroleum Engineers held inDallas, Tex., Oct. 6–9, 1991, that differential sticking occurs when adrill pipe, or logging tool, becomes embedded in mud filter cake andwhere the drill pipe or filter tool is held by the mud overbalancepressure. Once sticking has occurred, a large force is required to freethe drill pipe, even if the mud overbalance is removed. Such stickingcauses several hours of rig time being spent in attempting to free thedrill pipe. In severe cases, the drill pipe cannot be freed and the wellhas to be sidetracked or abandoned. In the disclosure, a laboratorymethod is disclosed for freeing differentially stuck pipes with sheerand changes are proposed to the mud chemistry. As disclosed in theSociety of Petroleum Engineers, Paper SPE14244, “A New Approach toDifferential Sticking” by J. M. Courteille and C. Zurdo, presented atthe 60_(th) Annual Technical Conference and Exhibition of the Society ofPetroleum Engineers held in Las Vegas, Nev., Sep. 22–25, 1985,differential sticking has a high risk of occurrence in deviated wellsand the paper describes recording the pressure at different points ofthe pipe/cake and cake/formation interfaces in a laboratory device. Itis also known from, for example, U.S. Pat. No. 4,811,800 to produce aflexible drill string member for use in directional drilling in whichthe member has a spirally-shaped outer surface so as to make the membermore flexible at traversing bends in boreholes. Such a member is formedfrom a steel tube which has the outer surface thereof machined to form aspiral. The wall thickness, therefore, varies.

U.S. Pat. No. 6,012,744 discloses a heavy weight drill pipe which alsoincorporates tubular members having spirally formed external surfacesand the spirally formed members are taught to reduce the chances ofdifferential pressure sticking of the pipe when the pipe is used in ahigh angle or horizontal well bore.

Forces involved in the occurrence of differential sticking aresubstantially proportional to the area of a drill string elementembedded in the filter cake. It will be understood by those skilled inthe art that the filter cake is formed on the borehole wall whendrilling through permeable formations. A reduction in the area ofcontact between the filter cake and the drill string element is thus amajor objective of the spirally formed external surface of the memberdisclosed in U.S. Pat. No. 6,012,744.

By using a spiral formation with a right hand thread, in high angleholes, cuttings may be lifted into the main stream of the flowing mudand such right hand spiral designs increase the load effective at thebit by “screwing” the string towards the bit end while cuttings thathave not been lifted into the main stream mud are pushed upwards alongthe low side of the hole in the manner of an Archimedian screw pump.

Such spirally formed members of the prior art have internalcross-sections which are cylindrical and with an outer surface ofvarying diameters which vary along the drill string longitudinal axis.The manufacturing process of drill string members such as drill pipes,intermediate weight drill string elements and heavyweight drill pipeelements, as well as drill collars having a non-circular cross-sectionfor at least a part of their axial length, requires costly andtime-consuming external removal of metal by milling. In addition,eventual drilling a long cylindrical bore may also be required whenusing an initially solid bar stock to produce the above-mentioneddevices.

SUMMARY OF THE INVENTION

The present invention seeks to provide a drill string member having anexternal surface of varying diameters which is more readily produced.

According to one aspect of this invention, there is provided a method offorming a drill string member including the steps of providing a former,providing a cylindrical member to be shaped in relationship with theformer, providing sealing means at opposing ends of the cylindricalmember and the former, and applying a pressure sufficient to plasticallydeform said cylindrical member against said former, whereby asubstantially constant wall thickness about the circumference of thecylindrical member is provided.

According to a feature of this invention, there is provided a method offorming a drill string member including the steps of providing anexternal cylinder, inserting a core in a cylindrical tubular member,said core having a desired shaped external surface for the walls of saidtubular member, locating the cylindrical tubular member and core in theexternal cylinder, sealing the tubular member at its remote ends,applying a pressure to an annulus formed between the cylinder and thetubular member sufficient to plastically deform the tubular memberagainst the externally shaped surface of the core, whereby the walls ofthe tubular member have a substantially constant thickness about theperiphery of the tubular member, and removing the seals and core.

According to another feature of this invention, there is provided amethod of forming a drill string member including the steps of providinga former having an internal surface corresponding to a shape to beformed, providing a cylindrical tubular member to be shaped inside saidformer, providing sealing means at opposing ends of the tubular member,applying a pressure to the inside of said tubular member sufficient toplastically deform said tubular member against the internal surface ofsaid former, whereby said deformed tubular member has a substantiallyconstant wall thickness about the circumference thereof.

Preferably, portions having a circular cross-section are located atopposing ends of the plastically deformed tubular member.

Preferably, the pressure applied is produced by one of hydro-forming andexplosive-forming.

Advantageously, after plastically deforming said tubular member it isheat treated to relieve stresses.

According to another aspect of this invention there is provided a drillstring member arranged to at least alleviate differential stickingand/or to facilitate the transport of cuttings in at least one of a highangle and a horizontal well bore including at least one tubular memberhaving a portion with a non-circular internal and externalcross-section, whereby a substantially constant wall thickness about thecircumference thereof is provided.

Preferably, opposing end portions of said non-circular portion areprovided having a substantially circular cross-section.

Advantageously, said non-circular portion has an undulating outersurface with crests and troughs extending across a longitudinal axis ofsaid member.

In a preferred embodiment, said crests and troughs form a spiral groovein a wall of said member.

Preferably, said spiral groove is a right hand spiral.

Alternatively, said crests and troughs extend along a longitudinal axisof said member.

Advantageously, tool joints are secured by, for example, frictionwelding to said circular end portions.

Advantageously, said member has two or more crests, advantageously threeto eight crests and, preferably, six crests are provided in a planetransverse to a longitudinal axis through said non-circular portion.

Advantageously, plural said tubular members are provided in a drillstring, each interconnected by an interconnecting member having asubstantially constant external diameter.

According to yet a further feature of this invention, said drill stringmember is used as one of a drill pipe, an intermediate weight drillpipe, a heavyweight drill pipe, a drill collar, and a wash-over pipe.

According to a further aspect of this invention there is provided adrill string member made as defined herein above and used to at leastalleviate differential sticking, said member being in accordance withsaid another aspect.

The drill string member of the present invention improves the transportof cuttings from downhole in at least one of a high angle and ahorizontal well bore, especially when formed in a spiral configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 shows a transverse cross-section through an apparatus for forminga drill string member in accordance with this invention in a first stepof formation,

FIG. 2 shows a further step in forming the drill string member inaccordance with this invention,

FIG. 3 shows another step in the formation of the drill string member inaccordance with this invention,

FIG. 4 shows a cross-sectional view of a drill string member formed inaccordance with this invention,

FIG. 5 shows a transverse cross-section through another apparatus forforming a drill string member in accordance with this invention in afirst step of formation,

FIG. 6 shows a further step of forming the drill string member using theapparatus of FIG. 5,

FIG. 7 shows a side view of plural drill string members each formed inaccordance with this invention mounted in situ in a drill string.

FIG. 8 shows a side view of a further drill string member formed inaccordance with this invention,

FIG. 9 shows another drill string member formed in accordance with thisinvention, and

FIG. 10 shows a longitudinal cross-section of the assembly shown in FIG.4.

In the FIGS. like reference numerals denote like parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1, 2 and 3 show stages in forming a drill string member inaccordance with a first embodiment of this invention.

FIG. 1 shows a cylindrical tubular member to be deformed and an axiallysplit core 2 is inserted into the member 1, the core being a formerhaving a desired external shape to which the member 1 is to be formed.The core 2 has a forming portion of the desired configuration withcircularly cross-sectioned opposing end portions, the outside diametersof which correspond substantially with the internal diameter of member1. The forming portion of the core may have peaks and troughs extendingsubstantially Parallel to the longitudinal axis of the core/tubularmember or, preferably, the peaks and troughs extend along and across alongitudinal axis of the core/tubular member in a spiral formation,advantageously a right hand spiral. The core 2 is arranged to fit insidethe inside diameter of the member 1, but is arranged that a formingnon-cylindrical section does not extend over the extreme ends of themember 1 so that the extreme ends remain unformed. The member 1 and core2 are inserted into a pressure chamber formed by a thick walled cylinder3 and seals 16 (shown in FIG. 10). Fluid, preferably liquid, is insertedinto the annulus between the member 1 and cylinder 3 and high pressureis applied so as to deform the member 1 inwardly to take the shape ofthe external surface of the core 2 (as shown in FIG. 2).

The seals and fluid are removed to provide the configuration shown inFIG. 3 and the core is then removed to provide the member shown in FIG.4.

Although the core is, preferably, a split core, it is to be understoodthat such a configuration is not essential, as will be understood bythose skilled in the art. Although a six-lobed cross-section for thecore is preferred, i.e. a core having six crests, it is to be understoodthat other configurations may also be desired it required. Thus, what isrequired is that at least one crest is provided, two crests being anellipse, three crests forming a triangular shape, four crests a square,etc., but it is desired that the form has well rounded edges.

The tubular member 1 is, thus, plastically deformed and, although in theembodiment above-described, the ends of the member 1 are not deformed,the whole of the member 1 may be deformed if desired.

Instead of hydro-deforming the tubular member 1, it may, alternatively,be explosively deformed.

After the step of FIG. 3, the tubular member 1 has a configuration, asshown in FIG. 4, and the member may be heat treated to relieve stressescaused by the forming process.

If the walls of the tubular member 1 are very thick, deforming atambient temperature may not be possible or may be possible only withvery expensive pressure pumping systems. In such instances, it may benecessary to heat the member 1 to reduce the forces required fordeformation.

The cylindrical ends of the member are threaded for connection to othertubular members of a drill string. The member 1 may be used as awash-over pipe for open-hole wash-over operations to avoid differentialsticking. Conventional wash-over pipe generally has a diameter which isvery close to a well diameter. The contact area between the pipe and thefilter cake, one of the factors determining the likelihood of the pipebecoming differentially stuck, is, therefore, drastically increased incomparison to smaller outside diameter tubular elements, As wash-overpipe made in accordance with the present invention considerably reducesthe contact area and, therefore, virtually eliminates the risk ofdifferential sticking when washing over a stuck drill string.

To prepare the formed pipe for further manufacturing steps, the wallthickness of the cylindrical end of the pipe (member 1) may be increasedby creating external and/or internal upsets. Such a process is usual indrill string manufacturing industry and is followed by heat-treating thepipe. The upset pipe may be threaded and used as special, tool jointlesstubular elements such as wash-over pipe.

In an alternative embodiment for forming a drill string member inaccordance with this invention, shown in FIGS. 5 and 6, the tubularmember 1, prior to deformation, is inserted into a thick walled former 5having an internal surface configured to the shape desired for themember 1. The ends of the member 1 are sealed and liquid 6 is pumpedunder high pressure into the member 1. It will be noted from FIG. 5 thatthe outside diameter of the member 1 abuts the crests of the internalshape of the former 5. The liquid is subjected to high pressure causingthe member 1 to plastically deform outwardly, as shown in FIG. 6, theseals and former are removed to provide a member, as previously shown inFIG. 4.

In another embodiment of the invention, male and female tool joints arefriction welded to opposing ends of the cylindrical portions of themember 1, preferably upset ends of the formed pipe body, therebycreating tubular drill string members such as drill pipe, heavyweightpipe and intermediate weight pipe elements. The tool joints may have thesame diameter or, for handling purposes, at least slightly largerdiameter than an adjacent cylindrical pipe section. The tool joints maybe larger, identical to or smaller in outside diameter than thenon-circular portion of the pipe body for drill pipe and heavy wallpipe. For larger outside diameter drill string elements, the outsidediameter should, preferably, be of the same diameter as the tool jointsor only slightly smaller than the tool joints (external pressure formedelements) or slightly larger than the tool joints (internal pressureformed elements) to reduce bending stresses and wear in the tool jointarea.

In general, the diameter of a circle inscribed in the cross-section ofthe non-circular section of the member 1 should be not smaller than theinside diameter of the tool joints. If the manufacturing process or thedesired external shape of the pipe should result in a smaller diameterof the inscribed circle, metal may need to be removed from the inside ofthe pipe by boring or on a lathe. A member so modified is intended to bewithin the scope of the present invention.

In some instances it may be necessary to cover the crests on someportions of the non-circular portion of pipe with a protective layer ofhard metal for increased wear resistance. Conversely, to obtain anevenly thick layer of hard metal, the outside diameter of the member maybe slightly reduced on a lathe prior to applying the hard metal layer. Amember treated in such a manner is also within the scope of the presentinvention.

Referring to FIG. 7, plural members 1, each formed in accordance withthis invention, are serially connected in a drill string. The uppermostmember 1 has a circular cross-section portion 8 having the sameconfiguration to the initial cylindrical tubular member beforedeformation and the deformed member has four lobes 9 each extendinglongitudinally of the member 1. A top, remote end of the member 1 has afemale top connection joint 7 secured to the member 1 by, for example,friction welding. The intermediate member 1 has a six-lobedconfiguration, each of which extend longitudinally of the member 1. Abottom member 1 has four lobes 11 which are helically formed about themember 1 and a male joint 12 is connected to one end of the bottommember 1 by, for example, friction welding. Each of the members 1 areinterconnected by mating threaded tool joints (not shown). Each of thelobe formations of the members 1 are formed in a manner described above.

In FIG. 8, a tubular member 1 has a circular cross-section portion 13forming an elevator and slip recess. The member 1 has six lobes 14 whichare indented from the initially provided cylindrical member and areformed in accordance with this invention.

The embodiment shown in FIG. 9 has a member 1 with a helical formationof six lobes 15 which are indented from the initially provided circularmember and are formed in accordance with this invention.

Thus, the present invention provides a less expensive manner of forminga drill string member which is useful for preventing differentialsticking.

1. A drill string member to at least alleviate one of differentialsticking and to facilitate the transport of cuttings in at least one ofa high angle and a horizontal well bore including a single tubularmember formed to have a portion with a non-circular internal andexternal cross section and opposing end portions of said non-circularportion having a substantially circular cross section, wherein saidnon-circular portion has undulating inner and outer surfaces with crestsand troughs extending across a longitudinal axis of said single tubularmember and a substantially constant wall thickness about thecircumference thereof is provided, wherein tool joints are secured byfriction welding to said circular end portions, and further wherein saidtubular member has a circular cross-sectioned portion provided betweensaid non-circular portion and an upper tool joint to form an elevatorand slip recess.
 2. A drill string member as claimed in claim 1, whereinsaid crests and troughs form a spiral groove in a wall of said singletubular member.
 3. A drill string member as claimed in claim 2, whereinsaid spiral groove is a right hand spiral.
 4. A drill string member asclaimed in claim 2, wherein said crests and troughs extend along alongitudinal axis of said single tubular member.
 5. A drill stringmember as claimed in claim 1, wherein said single tubular member has twoor more crests.
 6. A drill string member as claimed in claim 1, whereinsaid single tubular member has three to eight crests.
 7. A drill stringmember as claimed in claim 1, wherein said single tubular member has sixcrests in a plane transverse to a longitudinal axis through saidnon-circular portion.
 8. A drill string member as claimed in claim 1,wherein male and female tool joints are secured to the circular endportions at respective opposing ends of said member and plural saidsingle tubular members are provided in a drill string, eachinterconnected by inter-engagement of said male and female tool joints.9. A drill string member as claimed in claim 1, wherein said drillstring member is used as one of a drill pipe, an intermediate weightdrill pipe, a heavyweight drill pipe, a drill collar, and a wash-overpipe.
 10. A drill string member as claimed in claim 1, wherein the tooljoints have an outside diameter which is substantially the same as theoutside diameter of the non-circular portion.
 11. A drill string memberas claimed in claim 1, wherein the diameter of a circle inscribed in thecross-section of the non-circular portion is not smaller than the insidediameter of the tool joints.
 12. A drill string member as claimed inclaim 1, wherein at least some of the outer surfaces of the crests areprovided with a protective layer of hard metal to increase wearresistance.